MUSCULOSKELTAL SYSTEM Flashcards
ARE ADULT BONES STABLE?
NO, THEY ARE NOT STABLE INERT MATERIAL.
what are osteoblast cells in bones?
OSTEOBLASTS= BONE MAKERS produce bones, regenerates bones
what are osteoclast cells in bones?
OSTEOCLASTS: BONE BREAKERS, breaks down bones into its minerals and removes damaged bones
WHAT ARE OSTEOCYTES?
OSTEOCYTES ARE BONE MAINTAINERS: a mature bone cell, and they surround bones to protect them.
what are bones made from?
calcium crystals (hydroxyapatite) in osteoid matrix
how is the bone formed?
osteoblasts lay down osteoid.
calcification: the hardening of tissue by depositing calcium phosphate (hydroapatite)
what happens when osteoblasts mature?
they become immobilised (stops operating)
osteocyte maintains surrounding osteoid
how does bone resorption happen (breakdown from inner to outer bones and assimilation of old bone and laying of new bones cells)?
-osteoclasts secrete acid and enzymes
-acid dissolves calcium phosphate crystals
-enzymes degrade osteoid
-calcium and phosphate released from bone into blood
how does bones grow when increasing in width?
-osteoblasts lay down new bone on outer surface
-osteoclasts resorb bone in inner surface of cavity to out
minimises weight gain
how does bones grow when increasing in length?
osteoblasts lay down new bone at epiphyseal plate (end of shaft- long main part of bone)
in detail what happens in the epiphyseal plate when bones increase in length? (4)
CHONDROCYTES PRODUCE NEW CARTILAGE in epiphyseal plate
epiphyseal plate widens causing bone to lengthen
chondrocytes die
osteoblasts replace chondrocytes and lay down bone
when does epiphyseal plate closure happen?
at puberty:
girls: 13-15yrs
boys: 15-17 yrs
what are the 3 effects of abnormal growth hormone (GH) secretion?
- dwarfism
- gigantism
- acromegaly
what is dwarfism?
decreased GH secretion in children
what is gigantism?
increased GH secretion in children (pre-puberty)
what is ACROMEGALY?
INCREASED GH SECRETION IN ADULTS (not taller bit affects the visual characteristics of person like jaw growth, long face.)
what other hormones affect growth?
- thyroid hormones : rewired for synthesis of GH
- insulin: needed for cellular action of GH
- sex hormones: important in pubertal growth.
- Glucocortoids: inhibit growth, inhaler minimises effects of glucocortoids as not too much secreted at one go.
what are two bone diseases?
osteomalacia (rickets in children)
osteoporosis (epidemic levels)
what are 2 joint diseases?
- osteoarthritis
- gout
what is osteomalacia (rickets)?
deficiency in bone mineralisation –> softening and weakening of bones
what causes osteomalacia (rickets)?
dietary insufficiency (VITAMIN D2)
LACK OF SUNLIGHT (vitamin D3)
renal disease causing decreased calcitriol
what can osteomalacia rickets be treated by?
vitamin D :
Ergocalciferol (type of vitamin D found in food)
Calcitriol - if renal disease (active form of vitamin D made in the kidney which binds to and activates vitamin D receptors)
what causes osteoporosis?
-low bone density (loss of hydroxapatite)- from fall or incidence more likely for bones break more easily
-more common in elderly women
who is at most risk of osteoporosis- low bone density
post menopausal women
over 75 yrs
glucocorticoid induced
